For example, in the case in which an automobile is provided with an armrest-equipped seat equipped with an armrest, on which an arm or the like is reclined, the armrest is sometimes movable making allowance for sitting down and rising from the seat. Typically, this movable armrest is fixed almost horizontally to the side surface of the seat back when used. When stored, the movable armrest is lifted upwardly and fixed almost vertically to the side surface of the seat back.
The movable armrest has to be fixed so as not to easily move when used. When the movable armrest is stored because it is not used, the locked movable armrest in the use state once has to be unlocked from the fixed state, and is moved to a storage position.
As a device for releasing this fixed state, there is Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2000-500214 (PTL 1), for example. PTL 1 discloses a structure in which a rocking ratchet 6, which corresponds to a lock gear, swings at an axis 6A, which is a rotation center, and the ratchet 6 is fixed to lock a gear 6B.